homework

exercises/02_number/main.go

@@ -0,0 +1,23 @@
+package main
+
+import "fmt"
+
+func number(i int) {
+	if i <= 0 {
+		return
+	}
+	fmt.Printf("%v\n", i)
+	if i >= 1 {
+		number(i - 1)
+		fmt.Printf("%v\n", i)
+	}
+}
+
+//time complexity: O(n)
+//space complexity: O(n)
+
+func main() {
+	var i int
+	fmt.Scan(&i)
+	number(i)
+}

exercises/02_number/main_test.go

@@ -0,0 +1,28 @@
+package main
+
+func Examplenumber() {
+	number(11)
+	// Output:
+	// 	11
+	// 10
+	// 9
+	// 8
+	// 7
+	// 6
+	// 5
+	// 4
+	// 3
+	// 2
+	// 1
+	// 1
+	// 2
+	// 3
+	// 4
+	// 5
+	// 6
+	// 7
+	// 8
+	// 9
+	// 10
+	// 11
+}

exercises/03_fibonacci/main.go

@@ -0,0 +1,25 @@
+package main
+
+import "fmt"
+
+func fibonacci(n, el1, el2 int) {
+	if n != 0 {
+		fmt.Printf("%v\n", el1)
+		sum_el := el1 + el2
+		el1 = el2
+		el2 = sum_el
+		n--
+		fibonacci(n, el1, el2)
+	}
+}
+
+//time complexity: O(n)
+//space complexity: O(n)
+
+func main() {
+	var n, el1, el2 int
+	el1 = 0
+	el2 = 1
+	fmt.Scan(&n)
+	fibonacci(n, el1, el2)
+}

exercises/03_fibonacci/main_test.go

@@ -0,0 +1,16 @@
+package main
+
+func Examplefibonacci() {
+	fibonacci(10, 0, 1)
+	// 	Output:
+	// 	0
+	// 1
+	// 1
+	// 2
+	// 3
+	// 5
+	// 8
+	// 13
+	// 21
+	// 34
+}

exercises/04_is_power_of_two/main.go

@@ -0,0 +1,25 @@
+package main
+
+import "fmt"
+
+func power(n int) {
+	if n == 1 {
+		fmt.Println("Is power of two")
+		return
+	} else if n <= 0 || n%2 != 0 {
+		fmt.Println("Is not power of 2")
+		return
+	} else if n >= 2 {
+		n /= 2
+		power(n)
+	}
+}
+
+//time complexity: O(logn)
+//space complexity: O(logn)
+
+func main() {
+	var n int
+	fmt.Scan(&n)
+	power(n)
+}

exercises/04_is_power_of_two/main_test.go

@@ -0,0 +1,7 @@
+package main
+
+func Examplepower() {
+	power(14)
+	// Output:
+	// Is not power of 2
+}

exercises/05_sum_of_digits/main.go

@@ -0,0 +1,23 @@
+package main
+
+import "fmt"
+
+func sum(n, sum1 int) {
+	if n > 0 {
+		sum1 += n % 10
+		n /= 10
+		sum(n, sum1)
+		if n == 0 {
+			fmt.Println(sum1)
+		}
+	}
+}
+
+//time complexity: O(n)
+//space complexity: O(n)
+
+func main() {
+	var n, sum1 int
+	fmt.Scan(&n)
+	sum(n, sum1)
+}

exercises/05_sum_of_digits/main_test.go

@@ -0,0 +1,10 @@
+package main
+
+var sum1 int
+
+func Examplesum() {
+	sum(1112, sum1)
+	// Output:
+	// 1112
+	// 5
+}

exercises/06_max_num/main.go

@@ -0,0 +1,27 @@
+package main
+
+import "fmt"
+
+func max(s []int) (int, int) {
+	var min, max1, max2 int
+
+	if len(s) > 0 {
+		min = s[0]
+		max1, max2 = max(s[1:])
+	}
+	if min > max1 {
+		return min, max1
+	} else if min > max2 {
+		return max1, min
+	} else {
+		return max1, max2
+	}
+}
+
+//time complexity: O(n)
+//space complexity: O(n)
+
+func main() {
+	s := []int{23, 10, 15, 0, 9, 20, 10}
+	fmt.Println(max(s))
+}

exercises/06_max_num/main_test.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestMax(t *testing.T) {
+	for _, tc := range []struct {
+		s    []int
+		res1 int
+		res2 int
+	}{
+		{[]int{20, 40, 20, 11, 38}, 40, 38},
+		{[]int{10, 11, 13, 1, 2}, 13, 11},
+		{[]int{40, 40, 40}, 40, 40},
+		{[]int{10, 11, 13, 1, 2}, 13, 11},
+		{[]int{40, 10, 20, 20}, 40, 20},
+		{[]int{10, 11, 13, 1, 2}, 13, 11},
+		{[]int{40, 1}, 40, 1},
+		{[]int{10, 11, 13, 1, 2}, 13, 11},
+		{[]int{10, 11, 13, 1, 2}, 13, 11},
+		{[]int{-4, 2, 3}, 3, 2},
+	} {
+		if max1, max2 := max(tc.s); max1 != tc.res1 || max2 != tc.res2 {
+			t.Errorf("got = %v, %v, want = %v, %v", max1, max2, tc.res1, tc.res2)
+		}
+	}
+}

exercises/main.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"fmt"
+)
+
+func rearrange(s []int, pivot int) (i int) {
+	cnt, p := 0, s[pivot]
+	j := 0
+	for ; j < len(s); j++ {
+		if s[j] == s[pivot] {
+			cnt++
+		}
+		if s[j] < s[pivot] {
+			s[i], s[j] = s[j], s[i]
+			i++
+		}
+	}
+	s[i], s[len(s)-1] = s[len(s)-1], s[i]
+	if cnt == 1 && p != 0 {
+		for i := 0; i < len(s); i++ {
+			if s[i] == p {
+				s[i], s[pivot+1] = s[pivot+1], s[i]
+			}
+		}
+	}
+	return i
+}
+
+func main() {
+	s := []int{8, 4, 1, 0, 5, 9, 3, 7, 2, 6, 5}
+	fmt.Println(rearrange(s, 4), s) // Output: 5 [2 4 1 0 3 5 9 7 8 6]
+
+	s4 := []int{4, 4, 4, 4}
+	fmt.Println(rearrange(s4, 2), s4) // Output: 5 [2 4 1 0 3 5 9 7 8 6]
+
+	s0 := []int{0}
+	fmt.Println(rearrange(s0, 0), s0) // Output: 5 [2 4 1 0 3 5 9 7 8 6]
+
+	s2 := []int{9, 6, 1, 7, 5, 9, 6, 5, 2, 6}
+	fmt.Println(rearrange(s2, 9), s2) // Output: 4 [2 5 1 5 6 9 6 7 6 9]
+
+	s3 := []int{9, 6, 1, 7, 5, 9, 6, 5, 2, 0}
+	fmt.Println(rearrange(s3, 9), s3) // Output: 0 [0 6 1 7 5 9 6 5 2 9]
+}

exercises/main_test.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestRearrange(t *testing.T) {
+	for _, tc := range []struct {
+		s    []int
+		p    int
+		want int
+	}{
+		{[]int{8, 4, 1, 0, 5, 9, 3, 7, 2, 6}, 4, 5},
+		{[]int{9, 6, 1, 7, 5, 9, 6, 5, 2, 6}, 9, 4},
+		{[]int{9, 6, 1, 7, 5, 9, 6, 5, 2, 0}, 9, 0},
+		{[]int{1, 7, 2, 3, 5, 4, 8, 6}, 1, 6},
+	} {
+		got := tc.p
+		if got != tc.want {
+			t.Errorf("ERR: int(%b): got = %v, want = %v", tc.p, got, tc.want)
+		}
+	}
+}